Sherman had partially invested the city before the middle of December; but it was well fortified and he refrained from assault. General Hardee, sent by Hood from Tennessee, had command of the defenses, with about eighteen thousand men. And there was Fort McAllister on the Ogeechee, protecting the city on the south. But this obstruction to the Federals was soon removed. General Hazen's division of the Fifteenth Corps was sent to capture the fort. At five o'clock in the afternoon of the 13th Hazen's men rushed through a shower of grape, over abatis and hidden torpedoes, scaled the parapet and captured the garrison. That night Sherman boarded the _Dandelion_, a Union vessel, in the river, and sent a message to the outside world, the first since he had left Atlanta. Henceforth there was communication between the army and the Federal squadron, under the command of Admiral Dahlgren. Among the vessels that came up the river there was one that was received with great enthusiasm by the soldiers. It brought mail, tons of it, for Sherman's army, the accumulation of two months. One can imagine the eagerness with which these war-stained veterans opened the longed-for letters and sought the answer to the ever-recurring question, "How are things at home?" Sherman had set his heart on capturing Savannah; but, on December 15th, he received a letter from Grant which greatly disturbed him. Grant ordered him to leave his artillery and cavalry, with infantry enough to support them, and with the remainder of his army to come by sea to Virginia and join the forces before Richmond. Sherman prepared to obey, but hoped that he would be able to capture the city before the transports would be ready to carry him northward. He first called on Hardee to surrender the city, with a threat of bombardment. Hardee refused. Sherman hesitated to open with his guns because of the bloodshed it would occasion, and on December 21st he was greatly relieved to discover that Hardee had decided not to defend the city, that he had escaped with his army the night before, by the one road that was still open to him, which led across the Savannah River into the Carolinas. The stream had been spanned by an improvised pontoon bridge, consisting of river-boats, with planks from city wharves for flooring and with old car-wheels for anchors. Sherman immediately took possession of the city, and on December 22d he sent to President Lincoln this message: "I beg to present to you, as a Christmas gift, the city of Savannah, with one hundred and fifty heavy guns and plenty of ammunition, and also about twenty-five thousand bales of cotton." As a matter of fact, over two hundred and fifty guns were captured, and thirty-one thousand bales of cotton. General Hardee retreated to Charleston.